Apparatus for polishing optical flats



Aug. 21, 1945. P. KlRSCH 2,333,131

APPARATUS FOR POLISHING OPTICAL FLATS Filed Dec. 1, 1942 I a I 1 l /4 I I l I HI I I Q 2/ 21a. 3'! i 2 a- 20 INVENTOR- PHuL K H HTTZO YS Patented Aug. 21, 1945 APPARATUS FOR POLISHING or'rroar.

FLATS Paul Kirsch, Woodhaven, N. Y., asslgnor to 0. P.

Goerz American Optical Company, a corporation of New York Application December 1, 1942, Serial No. 467,486

7 Claims.

This invention relates to improvements in' apparatus for polishing optical flats, and is directed more particularly to apparatus for grinding or polishing flat surfaces on various types of work.

Obviously, grinding and polishing constitutes substantially the same process, the only difference being in the sizes of the carborundum, grit, emery or rouge used as the abrasive, andthe type of reaction member or lap to which the abrasive is applied.

Another object of the invention is the provision of a suitable holder for the work and a support for said holder which together form a gimbal adapted to be connected in driven relation to the oscillating arm of a grinding or polishing machine.

A further object of the invention is the provision of novel means in connection with the workholder forcausing one corner or one edge of the surface being worked, to grind or polish faster than the remainder of the surface, so as to correct or change the angular relation of the surface being polished. These means may, include a weight or weights adapted to be attached to the holder for exerting greater pressures on selected areas of the surface being ground or polished.

The present invention is directed to workholders adapted to be used in connection with grinding or polishing machines now known in the art, These holders are so arranged that the surface being ground or polished, freely assumes its proper relation with respect to the polishing lap or other abrasive-carrying member. This arrangement permits the resultant of the normal forces applied to the face being polished to be altered with respect to that face, thereby increasing the pressure on portions of that face, and causing the removal of material from said portions at a greater rate than elsewhere on the surface.

Another object of the invention is the provision, in a holder for polishing prisms or the like, of a body portion irregular in shape but having a plurality of walls at least partially embracing the prism, said holder having its weight substantially equally distributed in relation to the central shaft which is engaged by the oscillating arm of the grinding or polishing machine, and including means to alter this equal distribution of the holder, thereby insuring even polishing of the entire surface being polished.

In describing the invention, the embodiment herein shown and the modification thereof are given in connection with the grinding or polishing of prisms; but it must be understood that the apparatus herein shown and described can just as effectively be used for grinding or polishing other types of parts having flat surfaces.

Referring to the drawing:

Figure 1 is an elevation, partly in section, of one form of my new and improved holder for polishing prisms and other optical flats;

Figure 2 is an elevation, partly in section, taken at right angles to the view shown in Figure 1;

Figure 3 is a plan view of the prism holder per se;

Figure 4 is an elevation, partly in section, of a modified form of the invention; and

Figure 5 is a plan view of the prism hol-der per se.

A rotating plate I 0 carries the abrasive. When used for grinding, this plate may be made of metal, glass, or any other desired material having any desired degree of hardness.

Since the description is to be in connection with polishing of flat surfaces, and particularly optical flats, the plate It has its upper face coated with pitch or the like, designated by the numeral II.

This pitch surface may have a series of grooves l2 formed therein, and a second series at right angles thereto, thereby breaking'the surface up into a plurality of facets; or the surface of the pitch coating I I may be unbroken.

The fixture, generally designated by the numeral l5, has a shaft l3 extending therefrom and journalled in a boss ll formed on the end of a movable or oscillatable am It Such machines are well known in the art and need not be described in detail herein.

Rigidly secured to the shaft I3 is a ring-like member I! having aligned bearing holes l8 and [9 formed therein. The hole l8 has a shouldered fillister head screw 20 journaled therein, and the hole I9 likewise has a shouldered fillister head screw 2| journaled therein. The threaded ends of the screws 20 and 2| oppositely engage threaded holes in an annular member 22, which may, for convenience, be called a ring."

The ring 22 has oppositely disposed slots 23 and 24. The slots '23 and 24 are preferably formed by drilling and reaming holes in the ring 22, and thereafter milling slots from the lower edge into the hole, said slots being of the same width as the diameter of the holes. This forms slots having semi-circular termini, and these slots are degrees apart from the tappedholes 20'- and 2| engaged by the fillister head screws 20 and II respectively.

The prism holder generally designated by'the numeral 25, consists of a hollow rectangular frame 25. The interior walls of the opening in the hollow rectangle 25 may be shaped to conform to the shape of the prism to be mounted therein. For example, in Figure 2 it will be seen that the side wall 26 is substantially vertical, whereas the side wall 26 is angular with respect to the vertical.

Holders for other types of prisms may have all sides vertical, and yet others may have more than one side angular with respect to the vertical.

A threaded shaft 21 is mounted in one side of the rectangular member 26, and a similar threaded shaft 28 is mounted'in the opposite side of the rectangular member 26, said shafts being in axial alignment with each other. The shaft 21 carries a locating nut 29, and likewise the shaft 28 carries a locating nut 30, and the purpose of these nuts will presently be described.

The side member 3| carries set screws 32 and 33. These set screws may be provided with the usual hollow conical ends, and each of them carries a little disc 34 of fibre or plastic which prevents the metal of the screw from actually contacting the prism 35 when the latter is mounted in the holder.

The side member 36 likewise carries set screws 31 and 38. These set screws (four in number) engage the prism 35 at four different points and enable the operator to adjust the prism in the holder in any desired manner, and, as before stated, the fibre tips carried by these set screws prevent the metal of the screws from actually touching the glass and causing the same to scratch or break.

The rectangular holder 26 carries a plurality of upright pins 39, 40, 4| and 42. A plurality of weights, one of which is shown in dot-dash lines and designated by the numeral 43, are provided for enabling the operator to cause any corner of the prism to polish faster than the remainder of the surface. In case the operator wants one side of the prism to polish faster than the remainder of the surface, he places two such weights on the pins on the side where this effect is wanted. For

instance, if the operator wants the surface adjacent to the edge along the side carrying the shaft 21 to polish faster, he would place one weight on the pin 4| and another weight on the pin 42. On the other hand, if it was desired to have the surface adjacent to the comer nearest the pin 42 to polish faster than the rest of the surface, the operator would place one of the little weights on the pin 42.

Between the prism 35 and the wall 26 I place a strip of fibre 44; and between the prism and the wall 26 I place a strip of fibre 45. These fibre strips prevent the surfaces of the prism from actu ally coming in contact with the metal forming the holder. I have used other materials than fibre for this purpose, and in some instances have cemented the prisms in the holders with suitable cement.

The prism 35 is placed in the holder with the fibres 44 and 45 in place, and is then centralized laterally by means of the screws 32, 33, 31 and 38. This may be done before the holder is placed in the polishing fixture.

To place the holder in the polishing fixture, the operator raises the fixture l and the arm l6, and places the holder 25 in position on the lap so that when the fixture and the arm are let down,

the slot 23 engages one of the threaded shafts (say, shaft 21), and the slot 24 engages the other threaded shaft 28. The nuts 29 and 30 are then adjusted so as to prevent excessive end play without binding.

The machine may then be started up, whereupon the rotating plate I0 carrying the lap I, rotates and the movable arm l6 oscillates. A suitable mixture of rouge and Water is applied to the lap and the polishing is effected.

After a period of polishing, the operator may shut the machine down, raise the fixture and arm, and take out the holder to note the progress of the work, and, as pointed out above, the operator may apply weights, such as the weight 43, to the holder for causing the corner or surface which is not as thoroughly polished, to polish faster due to the presence of the weight.

I have found that after the operator uses my improved holder for a while, he becomes very skillful in detemiining whether to apply the weights or not and just where to apply them.

It is preferable to have the holder 25 in such form that the load or pressure of the prism on the lap II is normally as nearly uniform throughout its entire surface as possible.

In the modification shown in Figures 4 and 5, the fixture and the oscillating arm are given the same numerals; and likewise the rotating plate and the lap are given the same numerals as those described in connection with Figures 1, 2 and 3.

In this modification the member I1 is oppositely connected to a rectangular member 46, because the shape of the prism holder 41 makes a rectangular member preferable instead of a ring member such as the ring 22 described above. However, it may be stated that whether a ring or rectangle, octagon, etc., is used makes no difierence, just so this member can be oppositely engaged by screws or pins, such as the screws 20 and 2|, and may in turn oppositely engage shafts extending from the prism holder in the manner described above in connection with Figures 1, 2 and 3.

The prism holder 41 is formed to embrace and hold the prism 48 even though the latter be irregular in shape, keeping in mind that the mass of the holder should normally be equally distributed throughout the axial length and also throughout the width of the holder. For example, the width of the portion 41 is greater than the widths of the other portions of the holder; the widths of the portions 41 and 41 are less than that of 41 and these portions 41" and 41 are cut away, as shown at 49 and 50 in Figure 5, to maintain this balance.

Shafts 5| and 52 are oppositely mounted in the holder in axial alignment with each other, and these shafts are engaged respectively by slots 53 and 54 formed in the rectangular member 45. Screws 55 and 56 are mounted in threaded cross holes in the shafts 5| and 52 respectively for preventing excessive end' play of the prism holder 41 and the rectangular member 46 during the polishing process.

Fibre strips 51. are positioned between the prism 48 and the holder 41 to prevent axial contact between the glass and the metal, and suitable set screws 58 are provided for securing the prism in the holder. The set screws 58 may also be provided with soft tips for preventing the set screws from digging into the glass.

In placing the screws 55 and 56 in holes in the shafts 5| and 52 respectively, it will be noted that these screws are initially positioned so that the midportion of the surface of the prism being polished lies in the vicinity of the central vertical axis of the fixture (the shaft 3, for example), and if it is desired to have one portion polished faster than the other, the screws may be shifted to other holes so as to throw another portion of the area being polished on the center line. In other words, the position of the prism holder within the ring may be also adjusted in accordance with the portion of the surface to be polished faster. This may also be effected with the arrangement shown in Figures 1, 2 and 3, above described, by adjusting the nuts 29 and 30 along the shafts 21 and 28 respectively.

I havefound that the best results are produced when the oscillating arm I6 is substantially horizontal, and that the ring 22 in the first form described and the rectangle 46 in the second form described, must be substantially horizontal.

' thereof.

In the appended claims: the term "polishing is taken to mean grinding and/or polishing; the term prism will be taken to mean any piece of work held in the apparatus for the purpose of grinding and/or polishing a flat surface thereon; the term prism-holder" is taken to mean any fixture devised for holding the work, whether this work be a prism, a gauge block, or any other piece of work, a surface or surfaces of which are to be ground or polished; and the term "lap is taken to mean any member presenting a surface adapted to carry the abrasive and adapted to be engaged by the surface being worked.

Although I have herein shown and described a preferred form of my apparatus and a modification thereof, many changes may be made in the arrangements shown herein without departing from the spirit of the invention.

What is claimed is:

1. In apparatus for polishing prisms, a lap, a prism holder, a prism mounted in said holder and having a surface to be polished in contact with said lap, an oscillating arm, means connected to said arm and engaging said fixture for floatingly oscillating said fixture and the prism therein in contact with the surface of said lap, said holder having its mass so distributed that the contact pressure of the surface to be polished is substantially equal throughout the area of contact, and weight means adapted to be mounted on said holder for changing the distributed mass of the combination of said weight means and said holder, thereby changing the rate at which material is removed from corresponding portions of the surface of said prism.

2. In apparatus for grinding and/or polishing prisms, a lap, a prismholder adapted to support a prism with one surface thereof in contact with said lap, an oscillating arm, means connected to said arm and engaging said fixture for fioatingly moving said fixture over the surface of said lap,

and weight means adapted to be mounted on said holder for increasing the total mass and for changing the distribution of said mass in order to cause the grinding or polishing action to be greater on one portion of the surface than that on the remainder.

3. In apparatus for polishing optical flats, a work holder having side walls generally conforming to the shape of 'the work to be held, means for securing said work in said work holder, lap means, means for fioatingly moving said holder with one surface of said work in contact with said lapmeans, the mass of said holder being normally so proportioned that the weight of the holder and the work is substantially equally distributed over the surface of the work in contact with said lap means, thereby enabling a uniform polishing rate to be effected throughout said surface, and means for adding weight to a portion of said holder, thereby causing the polishing rate to be increased in corresponding portions of said surface.

4. In apparatus for grinding and/or polishing flat surfaces on pieces of work, a fixture and said holder being adapted to at least partially means to oscillate the same, a work-holder including extensions adapted to be engaged by said fixture and thereby form a gimbal, said holder having side walls generally conforming to the shape of said work, a re-action member adapted to have an abrasive supplied thereto, said member being engaged by the surface of the work to be ground or polished, the combined mass of the work and said holder being so proportioned that the mass is substantially equally distributed over the surface of the work in contact with said reaction member, and screw means carried by said extensions for moving the latter in said gimbal for upsetting the distribution of the mass over the surface of the work and causing a greater removal of material from a wanted portion of the surface.

5. In apparatus for grinding and/or polishing prisms, a lap, a prism-holder adapted to support a prism with one surface thereof in contact with said lap, an oscillating arm, means connected to said arm and engaging said fixture for floatingly moving said fixture over the surface of said lap, said holder being adapted to at least partially embrace the prism and having means to distribute its mass substantially equally with respect to a vertical axis passing through the midpoint of the area of the surface in contact with said lap, whereby the polishing action is substantially equal throughout the surface being polished, weight-engaging means carried on said holder, and weight means mounted on said weight-engaging means for changing the distri- "bution of the mass in order to cause the grinding or polishing action to be greater on one portion of the surface than on the remainder.

6. In combination with an optical grinding or polishing machine of the oscillator type, a work holder for holding the work in contact with a grinding or polishing surface, said work holder being attached to extensions forming a gimbal adapted to be attached to an oscillating member of said machine so that the overhanging weight of the oscillating member uniformly presses the surface of the work in operative engagement with the grinding or polishing surface, a plurality of vertical studs carried by said work holder and a plurality of weights having holes therethrough adapted to engage said studs whereby said weights may be selectively applied to said studs for altering the distribution of pressure over the surface of said workpiece for causing material to be removed in a corresponding area of the surface of said work.

7. In apparatus for grinding and/or polishing flat surfaces on pieces of worlna flat rotatable member adapted to carry an abrasive, anoscillatable arm, a gimbal ring, a yoke pivotally connected to said ring along a line extending through the axis thereof and having a vertical shaft extending therefrom operatively connected to said 10 arm, a work holder having oppositely disposed extensions pivotally mounted in said ring at right angles to said first line, a flat rotatable member adapted to carry an abrasive, said work holder carrying means for securing a piece of work therein, the weight of said oscillatable arm being the distribution of the pressurebver said surface.

PAUL mason. 

